#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	double i = 0;
	double sum = 0;
	double tol = 0;
	for (i = 1; i <= 100; i++)
	{
		double x = 1 / (2 * i - 1);
		sum += x;
	}
	for (i = 1; i <=100; i++)
	{
		double y = 1 / (2 * i +1);
		tol += y;
	}
	printf("%lf", sum - tol);
	return 0;
}